Are We Really Getting Smarter?

IQ tests aren't perfect, but they can be useful. If a boy doing badly in class does really well on one, it is worth investigating whether he is being bullied at school or having problems at home. The tests also roughly predict who will succeed at college, though factors like motivation and self-control are at least as important.

We are the first of our species to live in a world dominated by hypotheticals and nonverbal symbols.
Brian Stauffer

Quiz

An example of Raven's Progressive Matrices. Fill in the last shape.

Advanced nations like the U.S. have experienced massive IQ gains over time (a phenomenon that I first noted in a 1984 study and is now known as the "Flynn Effect"). From the early 1900s to today, Americans have gained three IQ points per decade on both the Stanford-Binet Intelligence Scales and the Wechsler Intelligence Scales. These tests have been around since the early 20th century in some form, though they have been updated over time. Another test, Raven's Progressive Matrices, was invented in 1938, but there are scores for people whose birth dates go back to 1872. It shows gains of five points per decade.

In 1910, scored against today's norms, our ancestors would have had an average IQ of 70 (or 50 if we tested with Raven's). By comparison, our mean IQ today is 130 to 150, depending on the test. Are we geniuses or were they just dense?

These alternatives sparked a wave of skepticism about IQ. How could we claim that the tests were valid when they implied such nonsense? Our ancestors weren't dumb compared with us, of course. They had the same practical intelligence and ability to deal with the everyday world that we do. Where we differ from them is more fundamental: Rising IQ scores show how the modern world, particularly education, has changed the human mind itself and set us apart from our ancestors. They lived in a much simpler world, and most had no formal schooling beyond the sixth grade.

The Raven's test uses images to convey logical relationships. The Wechsler has 10 subtests, some of which do much the same, while others measure traits that intelligent people are likely to pick up over time, such as a large vocabulary and the ability to classify objects.

Modern people do so well on these tests because we are new and peculiar. We are the first of our species to live in a world dominated by categories, hypotheticals, nonverbal symbols and visual images that paint alternative realities. We have evolved to deal with a world that would have been alien to previous generations.

More

Raven's Progressive Matrices are non-verbal multiple choice measures of the general intelligence. In each test item, the subject is asked to identify the missing element that completes a pattern. Click here to take the test.

A century ago, people mostly used their minds to manipulate the concrete world for advantage. They wore what I call "utilitarian spectacles." Our minds now tend toward logical analysis of abstract symbols—what I call "scientific spectacles." Today we tend to classify things rather than to be obsessed with their differences. We take the hypothetical seriously and easily discern symbolic relationships.

The mind-set of the past can be seen in interviews between the great psychologist Alexander Luria and residents of rural Russia during the 1920s—people who, like ourselves in 1910, had little formal education.

Luria: What do a fish and crow have in common?

Reply: A fish it lives in water, a crow flies.

Luria: Could you use one word for them both?

Reply: If you called them "animals" that wouldn't be right. A fish isn't an animal, and a crow isn't either. A person can eat a fish but not a crow.

Widespread secondary education has created a mass clientele for books, plays and the arts.

The prescientific person is fixated on differences between things that give them different uses. My father was born in 1885. If you asked him what dogs and rabbits had in common, he would have said, "You use dogs to hunt rabbits." Today a schoolboy would say, "They are both mammals." The latter is the right answer on an IQ test. Today we find it quite natural to classify the world as a prerequisite to understanding it.

Here is another example.

Luria: There are no camels in Germany; the city of B is in Germany; are there camels there or not?

Reply: I don't know, I have never seen German villages. If B is a large city, there should be camels there.

Luria: But what if there aren't any in all of Germany?

Reply: If B is a village, there is probably no room for camels.

The prescientific Russian wasn't about to treat something as important as the existence of camels hypothetically. Resistance to the hypothetical isn't just a state of mind unfriendly to IQ tests. Moral argument is more mature today than a century ago because we take the hypothetical seriously: We can imagine alternate scenarios and put ourselves in the shoes of others.

The following invented examples (not from an IQ test) show how our minds have evolved. All three present a series that implies a relationship; you must discern that relationship and complete the series based on multiple-choice answers:

1. [gun] / [gun] / [bullet] 2. [bow] / [bow] / [blank].

Pictures that represent concrete objects convey the relationship. In 1910, the average person could choose "arrow" as the answer.

In this question, the relationship is conveyed by shapes, not concrete objects. By 1960, many could choose semicircle as the answer: Just as the square is halved into a triangle, so the circle should be halved.

1. * / & / ? 2. M / B / [blank].

In this question, the relationship is simply that the symbols have nothing in common except that they are the same kind of symbol. That "relationship" transcends the literal appearance of the symbols themselves. By 2010, many could choose "any letter other than M or B" from the list as the answer.

This progression signals a growing ability to cope with formal education, not just in algebra but also in the humanities. Consider the exam questions that schools posed to 14-year-olds in 1910 and 1990. The earlier exams were all about socially valuable information: What were the capitals of the 45 states? Later tests were all about relationships: Why is the capital of many states not the largest city? Rural-dominated state legislatures hated big cities and chose Albany over New York, Harrisburg over Philadelphia, and so forth.

Our lives are utterly different from those led by most Americans before 1910. The average American went to school for less than six years and then worked long hours in factories, shops or agriculture. The only artificial images they saw were drawings or photographs. Aside from basic arithmetic, nonverbal symbols were restricted to musical notation (for an elite) and playing cards. Their minds were focused on ownership, the useful, the beneficial and the harmful.

Widespread secondary education has created a mass clientele for books, plays and the arts. Since 1950, there have been large gains on vocabulary and information subtests, at least for adults. More words mean that more concepts are conveyed. More information means that more connections are perceived. Better analysis of hypothetical situations means more innovation. As the modern mind developed, people performed better not only as technicians and scientists but also as administrators and executives.

A greater pool of those capable of understanding abstractions, more contact with people who enjoy playing with ideas, the enhancement of leisure—all of these developments have benefited society. And they have come about without upgrading the human brain genetically or physiologically. Our mental abilities have grown, simply enough, through a wider acquaintance with the world's possibilities.

—Mr. Flynn is the author of "Are We Getting Smarter? Rising IQ in the 21st Century" (Cambridge University Press).

WSJ opens select articles to reader conversation to promote thoughtful dialogue. See the 'Join the Conversation' area to the rightbelow for stories open to conversation. For more information, please reference our community guidelines. Email feedback and questions to moderator@wsj.com.